It is well known in the prior art that the automatic functioning of steam heated radiator plants can be used to provide a given comfortable temperature in the space to be heated by the radiators, such as the interior of an apartment of the like. It is also known that the automatic operation of the radiators should not only be dependent upon the interior temperature of the space to be heated but also depend upon outside climatic conditions.
The control of the heat radiators on the basis of the existing room temperature can take place individually for each radiator or in common for a group of such heat radiators by a thermostatically controlled valve which senses the inside temperature. However, it has been shown that there is a tendency for the inside temperature to change depending upon the outside climatic conditions. Thus, for instance, if the outside temperatures should suddenly get very low, the temperature inside of the area to be heated will have a tendency to be reduced rather quickly. When this condition occurs, it would be advantageous to be aware of the condition and to compensate for it. A prior art system which does this is manufactured by Dunham-Bush, Inc. of Marshalltown, Iowa and is called "Vari-Vac." With this system, stream is continuously supplied to the radiators but at a temperature and pressure which varies automatically with outside temperature and inside heat losses.
The outside conditions which have an influence on the rate at which the room temperature changes are the outside temperature, the degree of moisture in the outside air, sunshine, wind, rain, and snow. However, it should also be recognized that other climatic conditions may have a similar influence. Many systems have already been disclosed in which control units derive information relating to one or more of the above-mentioned conditions so that the control units of the heating system can be compensated for. Considering the fact that the outside temperature has a greater influence than any one of the other above-mentioned conditions, in this field of art it has become commonplace to represent one or more or all of the conditions with a measurement of the outside temperature, and this outside temperature will also be made use of in the present specification. However, the present invention should not be regarded as limited to the use only of the outside temperature for predicting changes in the inside temperature as mentioned above. Thus, even though the following specification uses the outside temperature as a demonstrative representation of any deliberate combination of indicators of the outside climatic conditions, the invention should not be regarded as limited to the use of the outside temperature only.